/**
 * Copyright 2010 Tim Down.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * jshashtable
 *
 * jshashtable is a JavaScript implementation of a hash table. It creates a single constructor function called Hashtable
 * in the global scope.
 *
 * Author: Tim Down <tim@timdown.co.uk>
 * Version: 2.1
 * Build date: 21 March 2010
 * Website: http://www.timdown.co.uk/jshashtable
 */

var Hashtable = (function () {
    var FUNCTION = "function";

    var arrayRemoveAt = (typeof Array.prototype.splice == FUNCTION) ?
        function (arr, idx) {
            arr.splice(idx, 1);
        } :

        function (arr, idx) {
            var itemsAfterDeleted, i, len;
            if (idx === arr.length - 1) {
                arr.length = idx;
            } else {
                itemsAfterDeleted = arr.slice(idx + 1);
                arr.length = idx;
                for (i = 0, len = itemsAfterDeleted.length; i < len; ++i) {
                    arr[idx + i] = itemsAfterDeleted[i];
                }
            }
        };

    function hashObject(obj) {
        var hashCode;
        if (typeof obj == "string") {
            return obj;
        } else if (typeof obj.hashCode == FUNCTION) {
            // Check the hashCode method really has returned a string
            hashCode = obj.hashCode();
            return (typeof hashCode == "string") ? hashCode : hashObject(hashCode);
        } else if (typeof obj.toString == FUNCTION) {
            return obj.toString();
        } else {
            try {
                return String(obj);
            } catch (ex) {
                // For host objects (such as ActiveObjects in IE) that have no toString() method and throw an error when
                // passed to String()
                return Object.prototype.toString.call(obj);
            }
        }
    }

    function equals_fixedValueHasEquals(fixedValue, variableValue) {
        return fixedValue.equals(variableValue);
    }

    function equals_fixedValueNoEquals(fixedValue, variableValue) {
        return (typeof variableValue.equals == FUNCTION) ?
            variableValue.equals(fixedValue) : (fixedValue === variableValue);
    }

    function createKeyValCheck(kvStr) {
        return function (kv) {
            if (kv === null) {
                throw new Error("null is not a valid " + kvStr);
            } else if (typeof kv == "undefined") {
                throw new Error(kvStr + " must not be undefined");
            }
        };
    }

    var checkKey = createKeyValCheck("key"), checkValue = createKeyValCheck("value");

    /*----------------------------------------------------------------------------------------------------------------*/

    function Bucket(hash, firstKey, firstValue, equalityFunction) {
        this[0] = hash;
        this.entries = [];
        this.addEntry(firstKey, firstValue);

        if (equalityFunction !== null) {
            this.getEqualityFunction = function () {
                return equalityFunction;
            };
        }
    }

    var EXISTENCE = 0, ENTRY = 1, ENTRY_INDEX_AND_VALUE = 2;

    function createBucketSearcher(mode) {
        return function (key) {
            var i = this.entries.length, entry, equals = this.getEqualityFunction(key);
            while (i--) {
                entry = this.entries[i];
                if (equals(key, entry[0])) {
                    switch (mode) {
                        case EXISTENCE:
                            return true;
                        case ENTRY:
                            return entry;
                        case ENTRY_INDEX_AND_VALUE:
                            return [i, entry[1]];
                    }
                }
            }
            return false;
        };
    }

    function createBucketLister(entryProperty) {
        return function (aggregatedArr) {
            var startIndex = aggregatedArr.length;
            for (var i = 0, len = this.entries.length; i < len; ++i) {
                aggregatedArr[startIndex + i] = this.entries[i][entryProperty];
            }
        };
    }

    Bucket.prototype = {
        getEqualityFunction: function (searchValue) {
            return (typeof searchValue.equals == FUNCTION) ? equals_fixedValueHasEquals : equals_fixedValueNoEquals;
        },

        getEntryForKey: createBucketSearcher(ENTRY),

        getEntryAndIndexForKey: createBucketSearcher(ENTRY_INDEX_AND_VALUE),

        removeEntryForKey: function (key) {
            var result = this.getEntryAndIndexForKey(key);
            if (result) {
                arrayRemoveAt(this.entries, result[0]);
                return result[1];
            }
            return null;
        },

        addEntry: function (key, value) {
            this.entries[this.entries.length] = [key, value];
        },

        keys: createBucketLister(0),

        values: createBucketLister(1),

        getEntries: function (entries) {
            var startIndex = entries.length;
            for (var i = 0, len = this.entries.length; i < len; ++i) {
                // Clone the entry stored in the bucket before adding to array
                entries[startIndex + i] = this.entries[i].slice(0);
            }
        },

        containsKey: createBucketSearcher(EXISTENCE),

        containsValue: function (value) {
            var i = this.entries.length;
            while (i--) {
                if (value === this.entries[i][1]) {
                    return true;
                }
            }
            return false;
        }
    };

    /*----------------------------------------------------------------------------------------------------------------*/

    // Supporting functions for searching hashtable buckets

    function searchBuckets(buckets, hash) {
        var i = buckets.length, bucket;
        while (i--) {
            bucket = buckets[i];
            if (hash === bucket[0]) {
                return i;
            }
        }
        return null;
    }

    function getBucketForHash(bucketsByHash, hash) {
        var bucket = bucketsByHash[hash];

        // Check that this is a genuine bucket and not something inherited from the bucketsByHash's prototype
        return (bucket && (bucket instanceof Bucket)) ? bucket : null;
    }

    /*----------------------------------------------------------------------------------------------------------------*/

    function Hashtable(hashingFunctionParam, equalityFunctionParam) {
        var that = this;
        var buckets = [];
        var bucketsByHash = {};

        var hashingFunction = (typeof hashingFunctionParam == FUNCTION) ? hashingFunctionParam : hashObject;
        var equalityFunction = (typeof equalityFunctionParam == FUNCTION) ? equalityFunctionParam : null;

        this.put = function (key, value) {
            checkKey(key);
            checkValue(value);
            var hash = hashingFunction(key), bucket, bucketEntry, oldValue = null;

            // Check if a bucket exists for the bucket key
            bucket = getBucketForHash(bucketsByHash, hash);
            if (bucket) {
                // Check this bucket to see if it already contains this key
                bucketEntry = bucket.getEntryForKey(key);
                if (bucketEntry) {
                    // This bucket entry is the current mapping of key to value, so replace old value and we're done.
                    oldValue = bucketEntry[1];
                    bucketEntry[1] = value;
                } else {
                    // The bucket does not contain an entry for this key, so add one
                    bucket.addEntry(key, value);
                }
            } else {
                // No bucket exists for the key, so create one and put our key/value mapping in
                bucket = new Bucket(hash, key, value, equalityFunction);
                buckets[buckets.length] = bucket;
                bucketsByHash[hash] = bucket;
            }
            return oldValue;
        };

        this.get = function (key) {
            checkKey(key);

            var hash = hashingFunction(key);

            // Check if a bucket exists for the bucket key
            var bucket = getBucketForHash(bucketsByHash, hash);
            if (bucket) {
                // Check this bucket to see if it contains this key
                var bucketEntry = bucket.getEntryForKey(key);
                if (bucketEntry) {
                    // This bucket entry is the current mapping of key to value, so return the value.
                    return bucketEntry[1];
                }
            }
            return null;
        };

        this.containsKey = function (key) {
            checkKey(key);
            var bucketKey = hashingFunction(key);

            // Check if a bucket exists for the bucket key
            var bucket = getBucketForHash(bucketsByHash, bucketKey);

            return bucket ? bucket.containsKey(key) : false;
        };

        this.containsValue = function (value) {
            checkValue(value);
            var i = buckets.length;
            while (i--) {
                if (buckets[i].containsValue(value)) {
                    return true;
                }
            }
            return false;
        };

        this.clear = function () {
            buckets.length = 0;
            bucketsByHash = {};
        };

        this.isEmpty = function () {
            return !buckets.length;
        };

        var createBucketAggregator = function (bucketFuncName) {
            return function () {
                var aggregated = [], i = buckets.length;
                while (i--) {
                    buckets[i][bucketFuncName](aggregated);
                }
                return aggregated;
            };
        };

        this.keys = createBucketAggregator("keys");
        this.values = createBucketAggregator("values");
        this.entries = createBucketAggregator("getEntries");

        this.remove = function (key) {
            checkKey(key);

            var hash = hashingFunction(key), bucketIndex, oldValue = null;

            // Check if a bucket exists for the bucket key
            var bucket = getBucketForHash(bucketsByHash, hash);

            if (bucket) {
                // Remove entry from this bucket for this key
                oldValue = bucket.removeEntryForKey(key);
                if (oldValue !== null) {
                    // Entry was removed, so check if bucket is empty
                    if (!bucket.entries.length) {
                        // Bucket is empty, so remove it from the bucket collections
                        bucketIndex = searchBuckets(buckets, hash);
                        arrayRemoveAt(buckets, bucketIndex);
                        delete bucketsByHash[hash];
                    }
                }
            }
            return oldValue;
        };

        this.size = function () {
            var total = 0, i = buckets.length;
            while (i--) {
                total += buckets[i].entries.length;
            }
            return total;
        };

        this.each = function (callback) {
            var entries = that.entries(), i = entries.length, entry;
            while (i--) {
                entry = entries[i];
                callback(entry[0], entry[1]);
            }
        };

        this.putAll = function (hashtable, conflictCallback) {
            var entries = hashtable.entries();
            var entry, key, value, thisValue, i = entries.length;
            var hasConflictCallback = (typeof conflictCallback == FUNCTION);
            while (i--) {
                entry = entries[i];
                key = entry[0];
                value = entry[1];

                // Check for a conflict. The default behaviour is to overwrite the value for an existing key
                if (hasConflictCallback && (thisValue = that.get(key))) {
                    value = conflictCallback(key, thisValue, value);
                }
                that.put(key, value);
            }
        };

        this.clone = function () {
            var clone = new Hashtable(hashingFunctionParam, equalityFunctionParam);
            clone.putAll(that);
            return clone;
        };
    }

    return Hashtable;
})();